1. Field of the Invention
The present invention relates generally to an apparatus which prepares for splicing webs (long flexible sheet materials such as plastic film, paper and foil) which are being transferred, and more particularly to web splicing preparation method and apparatus which are applied to a web feeding apparatus for a coater, a cutter, and so forth.
2. Description of Related Art
Japanese Patent Provisional Publication No. 62-285854 (hereafter referred to as "a prior art A"), Japanese Patent Publication No. 3-13144 (hereinafter referred to as "a prior art B") and Japanese Patent Provisional Publication No. 3-56348 (hereinafter referred to as "a prior art C") have disclosed preparing for splicing webs of new and old rolls together.
On the other hand, concerning techniques for estimating a residual length of a roll, Japanese Patent Publication No. 8-644 has disclosed an automatic paper splicing method, and Japanese Patent Provisional Publication No. 7-304561 has disclosed an apparatus for displaying a residual length of a roll. According to these techniques, a web feeding speed and a rotating speed of the roll are measured during the feeding, and then the diameter of the roll in use is calculated according to the above-mentioned speeds, and the residual length of the roll is calculated according to the calculated diameter of the roll, the diameter of the core of the roll and the thickness of the web.
In the case of a photosensitive material such as a roll of photographic printing paper, since a part which is adjacent to the seam of the spliced webs is sometimes put on the market, the web of the periphery of the original roll should be disposed before the splicing operation. The prior arts A, B and C have a disadvantage because an operator has to dispose the web of the periphery of the original roll.
A scrap web, which was the web of the periphery of the original roll and was cut off from the leading end of the new web, is rolled up to be a small roll so as to save a disposal space. The prior arts A, B and C have a disadvantage because the operator has to roll up the scrap web.
In the case of the rolls of photographic printing paper, the spliced parts of the new and old webs are overlapped and welded together by heat or ultrasonic vibrations. This splicing operation requires the positional accuracy of the spliced parts not only in a width direction but in a longitudinal direction. The prior arts A and B can secure the positional accuracy in the width direction of the leading end of the new web, but not in the longitudinal direction. The prior art A can secure the positional accuracy in the longitudinal direction of the leading end of the new web, but not in the longitudinal direction of the trailing end of the old web. In the prior art A, the splicing is performed by means of adhesive tape.
In the case of the rolls of photographic printing paper, it is necessary to punch a hole for indicating the seam, which is called an ISO hole, on the proximity of the seam of the new and old webs. In the prior arts A and B, the ISO hole cannot be punched in the proximity of the leading end of the new web before the splicing operation. The ISO hole can be punched only after the splicing operation, and thus splicing time is wasted.
The prior art A has a disadvantage in that the operator has to set a web holder, which pulls out the leading end of the new web from the new roll, at the leading end of the new web and recover the web holder and the scrap web after the splicing operation. In particular, the web holder must be recovered after the splicing operation every time the rolls are exchanged. In the prior arts B and C, the operator has to pull out the leading end of the new web from the new roll every time the rolls are exchanged.
In the prior art B, a part on the proximity of the leading end of the new web rubs against a suction conveyor when the web is positioned in the width direction. Then, there may be scratches, etc. on the part of the new web, and the part cannot be put on the market.
On the other hand, in the conventional roll residual length estimating method and apparatus, the diameter of the roll is calculated according to the web feeding speed and the rotating speed of the roll during the feeding. That is, the unevenness of the cores in diameter is not taken into consideration. Consequently, the residual length of the roll cannot be correctly determined due to the unevenness.
In the case of Japanese Patent Publication No. 8-644, the operator measures the diameter of the core every time so as to consider the unevenness of the cores in diameter. Then, the operator has to take the trouble of measuring the diameter of the core every time, and the time of operation of the apparatus is wasted. If the web is a photosensitive material such as photographic film and photographic printing paper, the apparatus is installed in a darkroom, and hence there are hazards connected with measuring the diameter of the core, and the measurement cannot be correctly performed.